Adjustable delay line



Nov. 10, 1953 5. J. JOHNSON 2,659,053

ADJUSTABLE DELAY LINE Filed July 8, 1952 42 a 44 l4- 0 r 40 74 4Q as soE FIG. 2

20 FIG 3 INVENTOR.

SVEN u. JOHNSON MW ATTO NEYS Patented Nov. 10, 1953 Andersen"Laboratories, 11:16:; West" Hartford, Gonn.;--acorporation ofGonn'ecticut Appliatioiijuly 8*, 1952, Semi N6; 297%? 12 Ola'ilil'sspresent invention relatests delay lines'of tl'i type-coniprisifig afisiiiittiri'fi ahd a-rfeeeiv ifigerystm for com 1 in a electricalcircuit and" having disposed tlierbtween an actuarc'all'ysuitable-materialcofiduetiveer ii-lti'asoriics'. The-"inventionparticularly concerned with a construction aridarrang'e t of theelements of aldelay line of the char cter referred to permits variationand adjustment of the length of the time delay of transmission tirfiebetween the transmitting and the r 'ceivihg' crystal.

As well known to those skilled-iii the of manufacturing and utilizingtime delays" of the type'referredto liere siich-tir'ne delays are ofcritical and sensitive construction and'the utmost care inu'stbetaken-to avoid rion=uniformity,-reflections and attenuation not only inthe various elements-themselves but particularly at the interfaces'therebe'tween; Furthermore, the precise dimensions of the variouselements are extremely critical and uniformity. of characteristicsis'ex' tremely' difficult to-atta'iri-i The principal object of thepresent invention is'to devise a construction for time delays'whieh willpermit adjustment thereof after assembly and which despite its uniqueadjustment feature will not be adversely afiected from the standpointofuniformity and attenuatiom A further objeot'of the invention istoprovide an adjustable time delay having desirable'per formance'characteristics without" using compli cated-and expensive mechanisms anddesigns;

Another objeotisto provide an adjustable time delay in which theadjustment operation is--simple and easy to perform with aminimum ofinstruction and experience;

Anotherobject of the invention is to provide an adjustable time delaywhich will operate satisfactorilyover longperiodsof-time without mal--=functioning and which will be comparatively giigg'ed iii constructionand foolproof inoperaion.

Other objects will be in fiart'dtvidus anolin part pointed-out more'mdetail hereinafter.

The inventionac'cor'diri'g'ly consists the fea tures or construction,combination of'lernefits' an arrangement of parts" which" win be"seenplifid in the construction Hereafter s'tfoith and thesc'cs'peer theappiieationtr wit to indicatedin the appended'olaili is;

Iiithe' drawing: p

I Fig. 1 is a plan vie or 'ffieliafiisin includingtheadjustable"delayliiie of the present invention;

Fig. stress-seamen view taken along the fine 2" 2of FIE. 1; and" Fig".3is" ai i nlargeddiagran mati c view of the operating elements of theadjustable delay line i a Rererr'm to the drawing,- th e basicinventionof uiesresest assiieaties is iiest'ii-iustiated m Fig.

quartz crystal It at] i com osed of aicdus'tiaF 1y suitable" iiiateria'lfor: conducting Inna-sonic In aceordanoe with the invention,- I have"dis= coveredthat iithe' 'crysta'ls It and It are disposed substantiallyparallel to each other and are inclined inwardly at asm'all anglevertical to the faces 22 and 24; and thebars' l venues are pressedtogether with a filn'tof iihctuousliiatefial there between; theultrasonic waves produced by one of these'crys'tals andtransfii-ittedinto its asso ciated bar of a'c'oustic material willsuccessfully pass through-the adjoining faces" of the bars M ail-dillandwill continue on through the other bar to" the othercrystalwithoutunczesir ble eiis' tortior1-,- reflection andattenuatioh;I have also found that this condition'will'existeven thougi'i one baris--movedlongitudinally with'respect' to the other withinreasonable-limiter a result of the ability: the device to trans mitultrasonic waves in an angular directio'n between separateside bysidebars of acoustic ma= terial without undesirable" attenuation anddis= tortion,-it is possible to vary theetfective-distance betweenthecrystals wand IG-an'd thusto vary or adjust the time periodfortransmission of the ul-trasomcs from one crystal to the other.RQI'EIllIlgto Figs.- l-and 2, there is shown one embodiment of amechanismfor adgustably inounting the arrangement shown in Fig.3 of therawing. The inbodiment shown in Figs. 1- and 2" is illustrativ'oi ly andmerely shows-one way to carry out thedhvention in: apractical man ner'.owever; it will Joe-readily apparent to one skilled the art thatthe-"mechanical arrangeiii'erit surmount-mg and adjusting the parts-ofthe delayline maybe subjectto a V wide variety of art and alls'uch'arraifigeirifits are intended-to be within: thes'op of theinvention.

hef erring'to Figs. 1 and Z, the-device is housed ing ofabottomplateBlip-frontplate 32-, and side plates 54 and at. Fixed to*theba'seplate at at the rear thereofis-a support 38in the form of a} meta-1m grfglor receiving eii'd or an singularly taiiii iasseseto; A secondcrystal i5- bar of rectangular cross section. The bar M of acousticmaterial, such as quartz, Invar, magnesium or the like, as previouslymentioned, is clamped to the supporting bar 38 by means of a clamp 40fixed to the bar by screws 42. The crystal I secured to the inclined endface l2 of bar i4 is connected by means of lead line 44 to the terminal46 by means of which the same may be connected to an electrical circuit(not shown). The opposite end of the acoustic bar [4 is preferablycurved as shown at 48 and this curved end 48 is preferably coated withsound absorbing material, such as collodion, etc., all of which aid inminimizing reflections.

The acoustic bar 20 and crystal l6 secured thereto are mounted on amovable supporting bar 50 and for convenience may be attached thereto bydisposing the same between a pin 52 and a plate insulator 54. The bar 20is similarly arcuate at the end 56 opposite from the crystal l6 and thiscurved end also is coated with sound absorbing material. The movablesupport bar 50 rests on the base plate 30 and is slidable along a guiderod 60. The guide rod 60 is urged rearwardly by a plurality of springs82 whereby it in turn urges the adjustable bar 50 and hence the acousticbar 20 toward the acoustic bar M with substantial force.

In order to adjust the longitudinal position of the movable bar 50 thesame is provided on its upper face with a rack 10 which meshes with apinion 12 on the end of a shaft 14 which is journaled in the opening 16in the front plate 32. The pinion I2 is urged into engagement with therack 10 by means of a leaf spring 18 bearing upon the upper surface ofthe shaft 14. This spring 18 also tends to prevent inadvertent movementof the shaft 14. The outer end of the shaft 14 is provided with a knob80 by means of which the shaft 14 may be manually rotated to adjust theposition of the acoustic bar 20.

The crystal [8 is connected by lead line 82 to a terminal 84. In orderto avoid any strain on the connection with the crystal Hi, the lead line82 may be supported in an insulator 86 supported on the end of themovable support bar 50.

As previously mentioned the crystals 10 and I6 are mounted substantiallyparallel to each other and at an angle vertical to the faces 22 and 24.The particular angle is not critical and will, of course, depend uponthe dimensions of the acoustic bars 14 and 20 and also on the amount ofvariation of adjustment required. For practical purposes, I have foundthat the disposing of the crystals at an angle of from 2 to degrees, forexample, will usually provide all of the adjustment required or desiredin most cases and will function satisfactorily.

While the acoustic bars 14 and are illustrated as being square in crosssection, this has been done merely as a matter of convenience. The crosssection of bars l4 and 20 is not critical, it being necessary only thatthey be provided with preferably fiat complementary parallel matingsurfaces 22 and 24.

The means by which the mating surfaces 22 and 24 are made to cooperatewith each other is believed to be a critical feature of the invention.It is possible to provide mating surfaces 22 and 24 such as by lappingtechniques which will conduct ultrasonic vibrations through theseparation, but this is not practical from the standpoint of producinguniform delay lines in large quantities at reasonable cost and, in anyevent, the

transmission is not at an optimum. However, by applying a viscous andflowable unctuous material to the mating surfaces 22 and 24,.a markedimprovement is noted in the manner in which the vibrations will besustained and the bars i4 and 20 may be longitudinally adjusted relativeto each other without difficulty. It is not desired to limit theinvention to the selection of any particular unctuous material since awide variety of such materials have been tested successfully. Ingeneral, preferred results are obtained when the unctuous material issomewhat sticky so that it will adhere to the faces 22 and 24 and it ispreferred to use a material which is stable and which will not evaporateor otherwise deteriorate or change over long periods of use. Asmentioned, the material must be viscous since in general liquids do nothave suflicient body to sustain shear ultrasonic vibrations. Similarly,the material must be flowable so as to permit sliding of the faces 22and 24 relative to each other and also, it is believed, so that it willtend to fill any irregularities between the surfaces. In general, any ofthe unctuous materials available commercially, such as mineral oilderivatives and synthetic resins, will sustain wave sound and thechemical composition does not appear to be critical. I have successfullyemployed such material as petrolatum, resins, and particularly theunctuous material sold under the trade name Vistac No. 1.

While the present invention is not necessarily limited to any particulartype of receiving and transmitting crystals, nonetheless, it isprincipally directed as a practical matter to delay lines employingcrystals of the shear type commonly referred to as Y-, AT-, or AC-cutcrystals. When shear type crystals are employed, the crystals arearranged so that the particle motion of the ultrasonic waves generatedis parallel to the faces 22 and 24.

With the arrangement as shown in the drawing, the distance between thecrystals 10 and I6 may be varied over wide limits without adverselyaffecting the acoustical and electrical characteristics of the deviceand there is thus provided an adjustable time delay suitable forpractical use in the art.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above descriptive or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the followingclaims is intended to cover all of the generic and specific features ofthe invention herein described and all statements of the scope of theinvention which, as a matter of language, might be said to falltherebetween.

I claim as my invention:

1. An adjustable ultrasonic delay line comprising a pair of side by sidebars formed of material acoustic-ally suitable for conducting sound inthe ultrasonic range, said bars being formed with complementary parallelmating surfaces, an unctuous material between the mating surfaces, atransmitting crystal aifixed to one end of one bar, and a receivingcrystal affixed to the opposite end of the other bar, said crystalsbeing substantially parallel and inclined at a small angle toward themating surfaces of the bars.

2. An adjustable ultrasonic delay line comprising a pair of bars formedof material acoustically suitable for conducting sound in the ultrasonicrange, said bars being mounted for relative longitudinal movement andhaving flat adjoining surfaces, a film of unctuous material between theadjoining surfaces, means for pressing the bars together, a transmittingcrystal aflixed to one end of one bar, and a receiving crystal aflixedto the opposite end of the other bar, crystals being substantiallyparallel and tilted inwardly at a small angle toward the said adjoiningsurfaces of the bars.

3. An adjustable ultrasonic delay line comprising a pair of bars formedof material acoustically suitable for conducting sound in the ultrasonicrange, means mounting the bars in parallel side by side relationship andpermitting relative longitudinal movement of the bars, the bars beingformed with flat longitudinally extending adjoining surfaces, meansbiasing said surfaces together, an unctuous material on said surfaces, afirst crystal affixed to one end of one bar, and a, second crystalafiixed to the diametrically opposite end of the other bar, saiddiametrically opposite ends having substantially flat parallel surfacesinclined inwardly toward the said adjoining surfaces at an angle of from2 to 15.

4. An adjustable ultrasonic delay line comprising a pair of bars ofuniform rectangular cross-section throughout, means for mounting thebars in side by side relationship and movable longitudinally relative toeach other, means for pressing the bars laterally together, an unctuousmaterial between adjacent surfaces of the bars, a first transducercrystal afiixed to one end of one bar, and a second transducer crystalafilxed to the diametrically opposite end of the other bar, saiddiametrically opposite end surfaces being substantially flat parallelsurfaces inclined inwardly at a small angle toward the other bar.

5. An adjustable ultrasonic delay line comprising a pair of generallyrectangularly shaped bars formed of material acoustically suitable forconducting sound in the ultrasonic range, means for mounting said barsfor relative longitudinal movement in parallel side by side relationshipwith adjacent surfaces engaging, a viscous flow-- able material betweensaid adjacent surfaces, each of said bars being formed with an angularly related end surface at one end, said bars being mounted with saidangularly related end surfaces diametrically opposite from each otherand inclined toward said adjacent surfaces of the bars, and a pair ofcrystals on said angularly related end surfaces.

6. An adjustable ultrasonic delay line as claimed in claim 5 in whichthe crystals are of the shear type and are arranged so that the particlemotion of the ultrasonic waves generated are parallel to said adjacentsurfaces of the bars.

7. An adjustable ultrasonic delay line comprising a pair of generallyrectangularly shaped bars formed of material acoustically suitable forconducting sound in the ultrasonic range, means for mounting said barsfor relative longitudinal sliding movement in parallel side by siderelationship with adjacent surfaces engaging, a viscous flowablematerial between said adjacent surfaces, each of said bars having arounded external corner at one end and an angularly related end surfaceat the'other end, said bars being arranged with the ends of one bardiametrically opposite from the similar ends of the other, and atransmitting and receiving crystal secured on the diametrically oppositeangularly related end surfaces of the bars.

8. An adjustable ultrasonic delay line as claimed in claim 7 wherein therounded external corners of the bars are coated with sound absorbingmaterial.

9. An adjustable ultrasonic delay line comprising a pair of generallyrectangularly shaped bars formed of material acoustically suitable forconducting sound in the ultrasonic range, said bars being arranged inparallel side by side relationship with adjacent surfaces engaging,means for pressing said bars together and for adjusting the barslongitudinally of each other, a viscous flowable material between saidadjacent surfaces, said bars being formed at diametrically opposite endswith parallel flat end surfaces inclined at a, small angle toward saidadjacent surfaces, and a transducer crystal secured to each of said endsurfaces.

10. An adjustable ultrasonic delay line comprising a pair of supportingmembers mounted for movement in a parallel direction relative to eachother, a pair of bars supported on said members in side by siderelationship, said bars having flat parallel engaging surfaces and beingformed of material acoustically suitable for conducting sound in theultrasonic range, a viscous flowable material between said engagingsurfaces of the bars, means biasing the supporting members together in alateral direction whereby said engaging surfaces of the bars are putunder pressure, said bars being formed with diametrically opposite fiatparallel end surfaces inclined at a small angle toward said engagingsurfaces, a crystal on each of said end surfaces, and means foradjusting said supporting members longitudinally of each other.

11. An adjustable ultrasonic delay line as claimed in claim 10 in whichthe means for adjusting said supporting members longitudinally of eachother comprises a control knob and gear means interconnecting the knoband one supporting member'including a rack fixed to said one supportingmember.

12. An adjustable ultrasonic delay line comprising a casing, a pair ofsupporting members mounted in the casing for longitudinal slidingmovement in a parallel direction relative to each other, spring meansbiasing the supporting members laterally toward each other, a pair ofgenerally rectangular bars of material acoustically suitable forconducting sound in the ultrasonic range disposed between the supportingmembers in side by side relationship with their adjacent surfacesengaging, each bar being fixed to the adjacent supporting member, anunctuous material between said adjacent surfaces of the bars. means formoving one of said supporting members longitudinally of the other, afirst quartz crystal affixed to one end surface of one of said bars, anda second quartz crystal afllxed to the diametrically opposite endsurface of the other of said bars, said end surfaces being substantiallyflat and parallel and inclined at an angle Name Date Arenberg June 20,1950 Number

